This invention relates to a wheel-supporting bearing having a built-in rotation sensor for detecting the wheel speed.
Unexamined Japanese Patent Publication 5-264562 discloses a wheel-supporting bearing including a rotation sensor for use with an antilock brake system (ABS).
Referring to FIGS. 5 and 6, the bearing proposed in this publication comprises a rotary bearing ring (outer ring) 41, a sensor rotor 43 mounted on the outer ring 41 for producing a magnetic field, a stationary bearing ring (inner ring) 42, and a rotation sensor 44 mounted on the inner ring 42, opposite to the sensor rotor 43. A seal member 45 is provided to seal the space between the outer peripheral surface of the rotation sensor 44 and the end of the outer ring 41.
The rotation sensor 44 comprises a stator 46 in the form of an annular case, and a coil 48 wound in an annular groove 47 formed in the stator 46. The stator 46 has a plurality of teeth 49 and 50 each corresponding to respective magnetic poles formed on the sensor rotor 43.
The stator 46 is formed by casting or by cold-forging a magnetic material such as metal. It is adapted to form a magnetic circuit around the coil 48 to produce an electromotive force by guiding a magnetic flux from the sensor rotor 43. The stator 46 has on its inner periphery an integral flange 51. When press-fitting the rotation sensor 44, the flange 51 serves as a stopper by abutting the end face of the bearing ring 42.
But mass-producing such stators by casting or forging requires a long time and high cost.
The voltage produced in the coil 48 has to be taken out. In the structure proposed in the above publication, the rotation sensor 44 is exposed to a rather harsh environment. It is therefore difficult to completely seal the joint portion between the lead extending from the coil 48 and the harness. If water leaks along the lead into the stator 46, or if the joint portion rusts, the sensor may suffer a drop in the output voltage or other trouble.
When mounting the rotation sensor 44 on the bearing ring 42, or otherwise handling it, undue external force may be applied to the joint portion between the lead extending from the coil and the harness. Thus, it is necessary to connect the lead to the harness with sufficient strength so that the joint portion can withstand such an external force.
An object of this invention is to provide a wheel-supporting bearing having a rotation sensor which can be manufactured at low cost and having a simple and strong structure for connecting the rotation sensor to the harness while providing a perfect seal at the joint portion therebetween.